Pdx-1 activates islet M-NM-1- and M-NM-2-cell proliferation via a TRPC3/6- and ERK 1/2-regulated mechanism
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ABSTRACT: The homeodomain transcription factor, Pdx-1, has important roles in pancreatic development and M-NM-2-cell function and survival. In the present study, we demonstrate that adenovirus-mediated overexpression of Pdx-1 in rat or human islets also stimulates cell replication. Moreover, co-overexpression of Pdx-1 with another homeodomain transcription factor, Nkx6.1, has an additive effect on proliferation compared to either factor alone, implying discrete activating mechanisms. Consistent with this, Nkx6.1 stimulates mainly M-NM-2-cell proliferation, whereas Pdx-1 stimulates both M-NM-1- and M-NM-2-cell proliferation. Furthermore, cyclins D1/D2 are upregulated by Pdx-1 but not by Nkx6.1, and inhibition of cdk4 blocks Pdx-1- but not Nkx6.1-stimulated islet cell proliferation. Genes regulated by Pdx-1 and not Nkx6.1 were identified by microarray analysis. Two members of the transient receptor potential cation (TRPC) channel family, TRPC3 and TRPC6, are upregulated by Pdx-1 overexpression, and siRNA-mediated knockdown of TRPC3/6 or TRPC6 alone inhibits Pdx-1-induced but not Nkx6.1-induced islet cell proliferation. Pdx-1 also stimulates ERK1/2 phosphorylation, an effect partially blocked by knockdown of TRPC3/6, and blockade of ERK1/2 activation with a MEK1/2 inhibitor partially impairs Pdx-1-stimulated proliferation. These studies define a pathway by which overexpression of Pdx-1 activates islet cell proliferation that is distinct from and additive to a pathway activated by Nkx6.1. We identified genes that were upregulated or downregulated at 48 h with Pdx-1 overexpression as compared to untreated and M-NM-2gal controls. We set up a microarray using primary rat islets that were left untreated or transduced with adenoviruses overexpressing M-NM-2gal or Pdx-1 for 48 h.
ORGANISM(S): Rattus norvegicus
SUBMITTER: Heather Hayes
PROVIDER: E-GEOD-49786 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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